Skin color variations are probably the most obvious difference within humans. It is known that the transcription factor MITF controls skin pigmentation by regulating the transcription of various pigmentation genes, such as TRP1, TRP2, and TYR. Altogether these genes alter the Pheomelanin (red pigment) to Eumelanin (black pigment) ratio of pigmented cells resulting in differently pigmented human skin. It is well known that skin types differ depending on the human's environment due to two reasons: Sufficient protection of UV light and Vitamin D production. Both factors are necessarily inversely correlated. Being perfectly adapted to their original habitat, the migration of people increased their risk of being maladapted and to develop skin cancer or Vitamin D deficiency.
Additionally, hyper- or hypopigmentary disorders are extremely common in the human population. Whereas minor, local changes are often well tolerated and accepted, major diseases usually display as disfiguring body condition with very limited treatment options.